textproduct: Rapid City

KEY MESSAGES

- Strong thunderstorms will linger into the overnight hours tonight. Main concerns will be heavy rain, gusty winds, and small hail. That being said, can't rule out an isolate storm cell that could produce severe wind gusts near 60 mph.

- Unsettled conditions with daily chances of showers and thunderstorms continue through much of next week.

UPDATE

Issued at 1038 PM MDT Sat May 30 2026

The bulk of the severe weather has passed. However, there are still some storms cells near central SD that are producing gusty winds. The other concern is flooding due to heavy rain so rainfall totals and rainfall rates will be closely watched overnight. But with the rain winding down, the risk of flooding will also go down.

For tomorrow, no big changes were made to the forecast. As was mentioned in the previous forecast discussion...Sunday will see the low (positioned over eastern MT) bring showers and isolated thunderstorms to northeast WY and portions of western SD. There is a marginal severe risk for portions of northwestern SD, however, severe weather is expected to be minimal for most of the region. Conditions are expected to improve throughout Sunday evening/night. There will be more chances for showers and thunderstorms almost everyday this coming week, with temperatures climbing back into the 90s by the end of the week.

DISCUSSION

(This Evening Through Saturday) Issued at 1220 PM MDT Sat May 30 2026

Current upper-air analysis and water vapor imagery depict large- scale ridging over central Canada, extending southward through MN and IA. Meanwhile, a negatively tilted trough stretches from the PAC NW into northern NV, with a upper-level low positioned over southwestern WY. Satellite imagery indicates increased WV flow into the region from the southeast, with 850mb dew points in the mid 50s. Cloud cover is decreasing over eastern WY and western SD. Radar returns show showers and isolated thunderstorms across portions of the region. Surface observations show temperatures ranging from the upper 60s to 70s, with dew points in the low 60s across the SD plains and drier air in the upper 40s to low 50s in WY. A dry line is situated southwest of the Black Hills, separating dew points in the 30s to mid 40s across southeastern WY and northeaster CO from the 50s to low 60s observed across the NE panhandle.

As cloud cover dissipates over western SD and northeast WY, the remnant capping inversion will erode, leading to increased thunderstorm development over the Black Hills, eastern WY, and the NE panhandle. Storms are currently developing over the Black Hills, with more expected to develop over far eastern WY and the NE panhandle along the dry line. CAMS are not in agreement on convective evolution, with some models (e.g. HRRR) showing development ahead of the squall line while other models keep the area clear (e.g. NAM Nest). A main factor that will determine if initiation occurs over the plains will be how quick cloud cover dissipates. The primary severe weather threats for today will be damaging winds and large hail, with an isolated spin-up tornado possible along the line. The severe threat is expected to continue until around midnight as the squall line tracks northeast into central SD, with storms gradually weakening below severe criteria as the line moves into a more stable airmass overnight. Sunday will see the low (positioned over eastern MT) bring showers and isolated thunderstorms to northeast WY and portions of western SD. There is a marginal severe risk for portions of northwestern SD, however, severe weather is expected to be minimal for most of the region. Conditions are expected to improve throughout Sunday evening/night. There will be more chances for showers and thunderstorms almost everyday this coming week, with temperatures climbing back into the 90s by the end of the week.

AVIATION

(For the 06Z TAFS Through 06Z Sunday Night) Issued At 1038 PM MDT Sat May 30 2026

Main aviation concerns are centered around the rain that will linger into the overnight and Sunday. Some CIG lowering in NE WY is possible Sunday afternoon, mainly after 12z with improvement after 20z. VIS concerns will be centered around the rainfall, heavier rates will reduce visibility, but outside of any rainfall, VIS should be VFR.

Wind speeds and directions shouldn't be a problem either with minor changes in direction due to the low spinning in the area but the speeds will be within a normal range for this area with gusts upwards of 20 to 30 kts.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.